Physical activity is vital to the normal growth of children and adolescence yet an epidemic proportion do not meet national physical activity guidelines, which in part has lead to the nation's most overweight and obese generation of children. School-sponsored physical activity has not been a solution in fighting the battle of inactivity among children and adolescents;thus, physical activity acquired during after-school hours is critical to the healthy development of children and adolescents. Youth sport is an after-school family-engaging health promoting activity with significant biopsychosocial benefits that can be a fun and enjoyable means of acquiring recommended levels of physical activity. In fact, youth sport programs create a broader community support for physical activity because they engage many stakeholders - children and adolescents, parents, coaches, and families creating a dynamic physical activity experience. However, attrition from youth sport is alarmingly high - as many as 1/3 of children drop out of youth sport annually and as many as 70% will drop out by adolescence. Therefore, research is needed to identify the determinants and barriers to sustained participation in youth sport. Concept mapping is an inductive mixed-methodology which simultaneously conceptualizes the experiences and barriers facing stakeholders by producing visual maps which display data about the major factors, how they are interrelated, similarities and differences among stakeholder groups, how factors change over time, and factors of greatest importance and feasibility for intervention. Further, concept mapping naturally leads to and guides evaluation metric development. The overall goal of this proposed study is to use concept mapping to develop a robust conceptual framework to further our understanding of underlying mechanisms related to best-practices and barriers in order to sustain the family and developing child's (8-18 years old) participation in youth sport. Consequently, to achieve our goals, our project is systematically organized into three phases, each addressing our study aims: (1) to identify factors and determine differences in how children, parents, and coaches conceptualize their experiences and barriers associated with their participation in youth sport;(2) to develop and validate objective multidimensional measures of participatory experiences and barriers in organized sport for the aforementioned stakeholders;and, in turn (3) to predict 1-year attrition from youth sport using these newly developed and validated measures of participatory sport experiences and barriers. This will be the first study to innovatively apply concept mapping to physical activity and sport participation research. Such unique data will be critical to the development of a youth sport sustainability model and will be instrumental in the design and testing of specific-developmentally and gender-appropriate efficacious youth sport sustainability interventions. Completion of our aims will further our ability to advance health promotion and disease prevention by furthering our understanding of how best to successfully engage children, their families, and communities in healthy and active lifestyles through organized youth sport. PUBLIC HEALTH RELEVANCE: Physical activity is vital to the normal growth and development of children and adolescents;however, an epidemic proportion of youth do not meet the minimum recommended physical activity guidelines which has resulted in the most overweight and obese generation of youth worldwide. One approach to addressing this public health crisis is by sustaining children's participation in organized youth sport, which is a family-engaging health promoting activity of which children derive significant biopsychosocial benefits. Successful completion of this project will advance scientific knowledge of determinants of youth sport attrition and further public health practice to promote and engage children, their families, and communities in healthy and active lifestyles through youth sport participation.